What causes obesity?

The reasons for obesity are many and complex. It is not simply a result of overeating. Research has shown that in many cases a significant, underlying cause of morbid obesity is genetic. Studies have demonstrated that once the problem is established, efforts such as dieting and exercise programs have a limited ability to provide effective long-term relief. Environmental factors, such as fast food, long days sitting at a desk, and suburban neighborhoods that require cars all magnify hereditary factors such as metabolism and efficient fat storage. Science continues to search for answers. But until the disease is better understood, the control of excess weight is something patients must work at for their entire lives.  more

The balance between calorie intake and energy expenditure determines a person's weight. If a person eats more calories than he or she burns (metabolizes), the person gains weight (the body will store the excess energy as fat). If a person eats fewer calories than he or she metabolizes, he or she will lose weight. Therefore the most common causes of obesity are overeating and physical inactivity. At present, we know that there are many factors that contribute to obesity, some of which have a genetic component: • Genetics. A person is more likely to develop obesity if one or both parents are obese. Genetics also affect hormones involved in fat regulation. For example, one genetic cause of obesity is leptin deficiency. Leptin is a hormone produced in fat cells, and also in the placenta. Leptin controls weight by signaling the brain to eat less when body fat stores are too high. If, for some reason the body cannot produce enough leptin, or leptin cannot signal the brain to eat less, this ...  more

Obesity occurs when a person consumes more calories from food than he or she burns. Our bodies need calories to sustain life and be physically active, but to maintain weight we need to balance the energy we eat with the energy we use. When a person eats more calories than he or she burns, the energy balance is tipped toward weight gain and obesity. This imbalance between calories-in and calories-out may differ from one person to another. Genetic, environmental, and other factors may all play a part. Genetic Factors Obesity tends to run in families, suggesting a genetic cause. However, families also share diet and lifestyle habits that may contribute to obesity. Separating genetic from other influences on obesity is often difficult. Even so, science does show a link between obesity and heredity. Environmental and Social Factors Environment strongly influences obesity. Consider that most people in the United States alive today were also alive in 1980, when obesity rates were lower. ...  more

In scientific terms, obesity occurs when a person's calorie intake exceeds the amount of energy he or she burns. What causes this imbalance between consuming and burning calories is unclear. Evidence suggests that obesity often has more than one cause. Genetic, environmental, psychological, and other factors all may play a part. Genetic Factors Obesity tends to run in families, suggesting that it may have a genetic cause. However, family members share not only genes but also diet and lifestyle habits that may contribute to obesity. Separating these lifestyle factors from genetic ones is often difficult. Still, growing evidence points to heredity as a strong determining factor of obesity. In one study of adults who were adopted as children, researchers found that the subjects' adult weights were closer to their biological parents' weights than their adoptive parents'. The environment provided by the adoptive family apparently had less influence on the development of obesity than the ...

Obesity occurs when a person consumes more calories than he or she burns. For many people this boils down to eating too much and exercising too little. But there are other factors that also play a role in obesity. These may include: • Age. As you get older, your body's ability to metabolize food slows down and you do not require as many calories to maintain your weight. This is why people note that they eat the same and do the same activities as they did when they were 20 years old, but at age 40, gain weight. • Gender. Women tend to be more overweight than men. Men have a higher resting metabolic rate (meaning they burn more energy at rest) than women, so men require more calories to maintain their body weight. Additionally, when women become postmenopausal, their metabolic rate decreases. That is partly why many women gain weight after menopause. • Genetics. Obesity (and thinness) tends to run in families. In a study of adults who were adopted as children, researchers found that ...  more

A. Obesity results when there is an imbalance between energy intake and energy expenditure. In other words, you consume more calories than you expend in your daily activities. There can also be medical causes for obesity, such as glandular irregularities. Many glandular problems are now medically treatable.  more

You can blame it on appetite, on depression, on addiction, but a team at the University of Michigan Medical School says that behind obesity there's just a protein in the brain's cells which plays a key role in the body's weight-regulating system, fat storage, sugar use and energy balance. The research team showed that the SH2B1 protein regulates the activity of the metabolic signaling molecules leptin and insulin, and the way the organism metabolizes the energy from food. The researchers even altered genetically the mice that presented a unique form of the SH2B1 protein in their brain cells. The investigators stopped the activity of this protein in the hypothalamus, the brain area used for eating, hunger, and energy balance.  more

In many ways, obesity is a puzzling disease. How the body regulates weight and body fat is not well understood. On one hand, the cause appears to be simple in that if a person consumes more calories than he or she expends as energy, then he or she will gain weight. However, the risk factors that determine obesity can be a complex combination of genetics, socioeconomic factors, metabolic factors, and lifestyle choices, as well as other factors. Some endocrine disorders, diseases, and medications may also exert a powerful influence on an individual’s weight. Factors which may influence the occurrence of obesity include, but are not limited to, the following: • genetics - Studies have shown that a predisposition toward obesity can be inherited. One study reported in 2004 found that 48 percent of children with overweight parents became overweight. Where a person carries weight - the hips or around the middle - is also strongly influenced by heredity. • metabolic factors - How a ...

Although some obesity is caused by underlying disorders, the main cause is probably lifestyle. The problem has two basic issues: too much food, too little activity. High calorie diets from processed foods and fats make it easy to add weight. Sedentary lifestyles without adequate exercise make it hard to take weight off. Evidence suggests that obesity has more than one cause: genetic, environmental, psychological and other factors may all play a part.  more